1. Field of the Invention
The present invention relates to a novel microorganism capable of accumulating a marked amount of glutamic acid by fermentation and a method for producing the desired product by culturing the microorganism.
2. Background of the Prior Art
In a method which comprises accumulating a marked amount of glutamic acid and collecting the same, namely, production of glutamic acid fermentation in an industrial scale, microorganisms capable of accumulating a marked amount of glutamic acid in medium, so called glutamic acid-producing bacteria, are cultured in a fermentation tank using an appropriate medium under suitably controlled culture conditions such as pH, temperature, amount of dissolved oxygen, etc. Many reports have been made on classification of glutamic acid-producing bacteria hitherto known and, for example, the following publications are given.
1. Kinoshita et al., Amino Acids, 2, 42 (1960) (hereafter referred to as Publication (1)) PA0 2. Okumura et al., J. Agr. Chem. Soc. Japan, 36, 141 (1962) (hereafter referred to as Publication (2)) PA0 3. Takayama et al., J. Agr. Chem. Soc. Japan, 39, 328 (1965) (hereafter referred to as Publication (3)) PA0 4. Takayama et al., J. Agr. Chem. Soc. Japan, 39, 335 (1965) (hereafter referred to as Publication (4)) PA0 5. Takayama et al., J. Agr. Chem. Soc. Japan, 39, 342 (1965) (hereafter referred to as Publication (5)) PA0 6. Komagata et al., J. Gen. Appl. Microbiol., 15, 243 (1969) (hereafter referred to as Publication (6)) PA0 7. Yamada et al., J. Gen. Appl. Microbiol., 16, 103 (1970) (hereafter referred to as Publication (7)) PA0 8. Yamada et al., J. Gen. Appl. Microbiol., 16, 215 (1970) (hereafter referred to as Publication (8)) PA0 9. Yamada et al., J. Gen. Appl. Microbiol., 18, 399 (1972) (hereafter referred to as Publication (9)) PA0 10. Yamada et al., J. Gen. Appl. Microbiol., 18, 417 (1972) (hereafter referred to as Publication (10))
In these reports, the glutamic acid-producing bacteria are not necessarily defined strictly to be bacteria capable of accumulating a marked amount of glutamic acid in medium. However, as a measure for the production amount, the glutamic acid-producing bacteria are reasonably interpreted to refer to industrially utilizable microorganisms capable of accumulating at least 30 g/l of glutamic acid in a medium in a yield of at least 30% based on glucose, as described in Publication (1).
These known glutamic acid-producing bacteria are all aerobic, gram-positive and non-sporeforming rods and classified in a bacterial group named coryneform bacteria. In addition, there are known facts regarding morphological properties and physiological and biological properties including that they are capable of accumulating a marked amount of glutamic acid in a medium, are biotin auxotrophic, contain mesodiaminopimelic acid in cell walls and have GC content of about 55% in DNA are similar to each other, etc. From these facts, it is widely admitted that known microorganisms called glutamic acid-producing bacteria are taxonomically akin to each other. In spite of the fact that they are considered to be microorganisms akin to each other, known glutamic acid-producing bacteria are identified to be in different genera such as the genus Brevibacterium, the genus Corynebacterium, the genus Microbacterium, etc. A major cause for this phenomenon of giving various classifications is believed to be earlier practices in identification which was made, inter alia, on a different classification system and a classification standard of the newest version of Bergey's Mannual of Determinative Bacteriology at that time, which is the most authoritative identification book for bacteria in the world, a difference in an identifier's weight on classification standard, etc. Further Kinoshita et al. (Publication (1)) made taxonomical research on approximately 20 glutamic acid-producing bacteria and using common properties possessed by these bacteria as the classification standard, proposed to create the genus of glutamic acid-producing bacteria. However, this proposal has not been adopted widely to date.
In production of glutamic acid by fermentation in an industrial scale, the aforesaid glutamic acid-producing bacteria are cultured in a medium containing components such as glucose, sucrose, acetic acid, etc. under aerobic conditions, using ammonia, urea, ammonium sulfate, etc. as nitrogen sources to accumulate a marked amount of glutamic acid in a medium. The amount of glutamic acid to be accumulated varies depending upon composition of medium, pH for incubation, culture temperature, amount of dissolved oxygen, means for secreting the glutamic acid produced in cells into medium, etc. However, by setting forth these factors in optimum ranges, glutamic acid can be accumulated in a yield of 30% or more based on glucose in a concentration of accumulated glutamic acid of 30 g/l or more.
Glutamic acid has been industrially produced by the fermentation method described above not only in Japan but also in many other countries. In the industrial production, one of the most important factors is high production rates. The present invention is to provide a highly economical technique for producing glutamic acid by fermentation in an industrial scale.